Stabilized silver halide emulsions



United States Patent 3,236,652 STABILIZED SILVER HALIDE EMULSIONS Kenneth C. Kennard and Frederick J. Russell, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Jan. 10, 1963, Ser. No. 250,490 7 Claims. (Cl. 96109) This invention relates to photographic compositions, and more particularly, to photographic silver halide emulsions containing addenda that have improved stability against fogging and desensitization due to metal contamination.

Photographic silver halide emulsions are easily fogged and desensitized with even trace amounts of metals such as copper, tin, iron and the like. Industrial X-ray films are frequently prepared with lead screens in contact with the silver halide emulsion. Lead oftentimes contains small amounts of tin which has a fogging eflect on the emulsion. Also small amounts of iron from manufacturing equipment and such conventional photographic supports as cellulose acetate tend to contaminate many commercial photographic elements. Further, manufacturing personnel in the photographic industry are continually coming in contact with brass fittings that contain copper and copper pocket coins, such cont-act being sufficient to cause undesirable fingerprints when the photographic film is being handled. X-ray films are frequently manually processed and fogging in the form of fingerprints is quite common.

Accordingly, it is an object of this invention to provide novel photographic silver halide emulsions having improved resistance to fogging and desensitization in the presence of such metals as copper, tin, iron and the like.

It is another object of this invention .to provide novel photographic silver halide emulsions containing stabilizing addenda that do not objectionably desensitize the emulsion.

It is also an object of this invention to provide new photographic silver halide emulsions containing stabilizing addenda that do not form insoluble precipitates or sludges in developers and fixers.

It is likewise an object of this invention to provide new photographic silver halide emulsions containing dihydroxy stabilizing addenda, and which addenda are not silver halide developing agents.

These and other objects of the invention are accomplished by incorporating into photographic silver halide emulsions stabilizing amounts of aryl compounds containing two adjacent hydroxyl radicals and at least one sulfo radical.

The aryl stabilizing addenda of the invention suitably comprise phenyl or naphthyl radicals containing two adjacent hydroXyl radicals and at least one sulfo radical. Water-soluble salts of the present addenda such as alkali metal salts (e.g., sodium and potassium) and ammonium salts are utilized to facilitate their incorporation in photographic emulsions in accordance with usual practice.

3,236,652 Patented Feb. 22, 1965 Typical stabilizing addenda of the invention have the formulas I OH and

wherein X and Y represent a sulfo radical or a hydrogen atom, at least one of X and Y being a sulfo radical. Illustrative stabilizing addenda of the invention include: 3,5-disulfocatechol disodium salt, 2,3-dihydroxy-7-sultonaphthalene sodium salt, 4-sulfocatechol ammonium salt, 2,3-dihydroxy 6,7 disulfonaphthalene potassium salt, and the like.

The amount of the subject stabilizing addenda that is used in the photographic silver halide emulsions of the invention can be widely varied. Generally, about .25 to 20 grams of the stabilizing addenda per mole of the silver halide in the emulsion are utilized, although the preferred concentration range is about 1 to 8 grams of the stabilizing addenda per mole of silver halide in the emulsion.

"the stabilizing addenda of the invention can be added to photographic silver halide emulsions utilizing any of the Well-known techniques in emulsion making. For example, they can be dissolved in a suitable solvent and added to the silver halide emulsion, or they can be added to the emulsion in the form of a dispersion similar to the technique utilized to incorporate certain types of color-forming compounds (couplers) in photographic emulsions. Techniques of this type are described in US. Patents 2,322,027 and 2,801,171. The solvent should be selected so that it has no harmful elfect upon the emulsion in accordance with usual practice, and generally, solvents or diluents that are miscible with water are a preferred.

Commonly employed photographic silver halides are utilized in the emulsion. Typical silver halides include silver chloride, silver bromide, silver iodide, silver chloroiodide, silver bromoiodide, silver chlorobrornoiodide and the like.

In preparing the present photographic emulsions, a Wide variety of hyd-rophilic dispersing agents or substrates (for the silver halide can be employed. Gelatin is preferred, although other colloidal materials such as colloidal album-in, cellulose derivatives, or synthetic resins such as polyvinyl compounds can be utilized. Such hydrophilic colloids are well known in the photographic art.

The subject photographic silver halide emulsions can contain the addenda generally utilized in such products including optical sensitizers, speed-increasing compounds, coating aids, hardeners, plasticizers, ultraviolet absorbers and the like addenda.

The above-described emulsions of the invention can be coated on a wide variety of photographic emulsion supports in accordance with usual practice. Typical supports include cellulose nitrate film, cellulose acetate film, polystyrene film, polyethylene terephthalate film, polyethylene film, polypropylene film, paper, polyethylenecoa-ted paper and other well-known supports.

When the above-described stabilizing addenda are incorporated in photographic silver halide emulsions, the resulting emulsions are less susceptible to fogging or desensitization due to contaminating metals that normally readily fog or desensitize photographic emulsions. The emulsions of the invention are particularly useful for reducing fog formation caused by copper, tin and iron contaminants. The subject stabilizing addenda are further characterized as not adversely alfecting the sensitometric properties such as speed and fog of silver halide emulsions and not forming objectionable insoluble precipitates or sludges with developers and fixers during processing.

Such well-known sequestering agents as ethylenediaminetetraacetic acid salts, while not desensitizing or reducing the spec-d of silver halide emulsions, tend to actually promote fogging of the emulsion in the presence of contaminating metals such as copper. Such sequeslterants as 8-hydroxyquinoline, 4,7-dimethyl-1,l-phenanthroline, 3,5,6,8-tetramethyl-1,10-phenanthroline, and sodium anthraquinone sulfonate desensitize photographic silver halide emulsions to an undesirable degree. The sequestering agent, N,N-dihydroxyethyl-N,N-dicarboxymethylethylenediamine, while not objectionably desensitizing silver halide emulsions, causes such a high degree of fog that it is not a practical photographic emulsion addenda. Further, we have found that several compounds closely related to the present stabilizing addenda are not as effective for the present purposes as the present addenda, as they tend to either desensitize or promote fogging of silver halide emulsions, such ineffective closely related compounds include 1-hydroxy-4-sulfonaphthalene sodium salt and 1,8-dihydroxy-3,6-disulfonaphthalene disodium salt. Hence, it was quite unexpected that the present specific class of stabilizing addenda as defined above could be effectively utilized in photographic silver halide emulsions to reduce fogging or desensitization due to metal contaminants, and which addenda do not objectionably desensitize or contribute to fogging of silver halide emulsions.

The invention is further illustrated by the following examples of preferred embodiments thereof.

EXAMPLE 1 Into a photographic sulfur-gold sensitized gelatinosilver bromoiodide emulsion of the type utilized in X-ray film was incorporated 3,5-disulfocatechol disodium salt in amounts of 1.5 and 6.0 grams per mole of silver halide in the emulsion. A similar emulsion was prepared without the 3,5-disulfocatechol disodium salt addendum. The various emulsions were then coated on cellulose acetate film supports in the usual manner. The sensitometric properties of the prepared photographic elements were determined, both initially, and after one weeks storage at 120 F. and 50% relative humidity by exposing the elements in the form of film strips in an Eastman Type Ib sensitometer, developed for 3 minutes at 68 F. and then fixed in hypo, washed and dried in the usual manner. The developer used had the following formula:

Developer A N-methyl-p-aminophenol sulfate 2.2 Sodium sulfite, anhydrous 72.0 Hydroquinone 8.8 Sodium carbonate, anhydrous 130.0 Potassium bromide 4.0

Water to make one liter.

Table A below summarizes the results of the sensitometric tests. In Table A, the speeds indicated are a function of the exposure necessary to give a density of 0.3 above background fog and are expressed as a reciprocal relation to exposure, the initial control speed being taken as 100. The concentrations of addenda are indicated in Table A as grams of addenda per mole of silver halide in the emulsion being tested.

As can be observed from the data set out in Table A, the 3,5-disulfocatechol disodium salt addendum of the invention did not adversely affect the sensitometric properties of the emulsion. The prepared photographic elements containing the above-described emulsions were subjected to a Fingerprint Test. In the Fingerprint Test, a fingerprint of a laboratory worker was made on each of the test films after the finger had been drawn across a strip of polished copper wet with distilled water, the films developed for 5 minutes at 68 F. in Developer B below and then fixed in hypo, and washed and dried in the usual manner.

Developer B Part 1:

Potassium hydroxide (45%) ml 7.0 Sodium bisulfite g 12.0 Potassium bromide g 8.0 Potassium iodide g 0.01 Water to make 50 ml.

Part 2:

2-methylaminoethanol sulfur dioxide addition product (17.8% S0 g 35.35

Z-methylaminoethanol g 2.27 4,4-dimethyl-l-phenyl-3-pyrazolidone g 0.36 Hydroquinone g 10.79 Water to make 50 ml.

(50 ml. of Part 1 and 50 ml. of Part 2 are combined and diluted to one liter with water prior to use.)

On development of the test films, the control sample containing no addenda of the invention produced a dense silver image the size of the fingerprint. The test sample containing 1.5 grams of the 3,5-disulfocatechol disodium salt per mole of silver halide on development produced a barely visible fingerprint silver image. The test sample containing 6.0 grams of the 3,5-disulfocatechol disodium salt per mole of silver halide on development produced a sample free of a fingerprint image.

EXAMPLE 2 Several samples of photographic sulfur-gold sensitized gelatino-silver bromoiodide emulsions of the type utilized in X-ray film containing other addenda of the invention were coated on cellulose acetate film supports. The resulting films were exposed in a sensitometer and processed as described in Example 1 except that both Developers A and B were utilized as indicated in Tables B and C below summarizing the results of the tests.

TAB LE B Cone. of Addenda (g./mle

(Developer A used) Fresh Test Addenda Speed '7 Fog ('4) Control 0 4-sulfocatechol ammonium salt 1. 5

TABLE Cone. of Addenda (g. lmole AgX) (Developer A used) Fresh Test Addenda Speed 7 Fog sodium salt As indicated by the data in Tables B and C, the addenda of the invention did not objectionably affect the sensitometric properties of the silver halide emulsion. When the photographic elements containing the addenda as described in Tables B and C were subjected to the ingerprint Test described in Example 1, no discernible fingerprint fogging resulted on the developed samples. However, a dense silver image the size of the fingerprint did result on development of the control sample.

EXAMPLE 3 The effect of 3,5-disulfocatechol disodium salt as an agent to eliminate desensitization caused by an iron contaminant in a photographic element was demonstrated by coating on a cellulose acetate film support a gelatin layer containing iron powder (2.5 to 5 microns) at a coverage of 0.2 mg. of iron per square foot and 90 mg. of gelatin per square foot, and over which was coated a gelatino-silver bromoiodide emulsion at a silver coverage of 910 mg. per square foot. In another similarlyprepared film sample, the gelatino-iron powder layer contained 3 grams of 3,5-disulfiocatechol disodium salt per mole of silver halide in the photographic element. The prepared photographic element containing the 3,5- disuliocatechol disodium salt of the invention was substantially free of fog in the areas containing the iron powder, while the photographic element not containing the 3,5-disulfocatechol disodium salt was 'heavily desensitized in the areas containing the iron powder on developing in Developer A as described in Example 1.

EXAMPLE 4 For comparative purposes, the well-known metal chelating agent, ethylenediaminetetraacetic acid tetrasodium salt and two compounds closely related to the addenda of the invention, namely, 1-hydroxy-4-sulfonaphthalene sodium salt and 1,8-dihydroxy-3,6-disulfonaphthalene disodium salt, were incorporated into photographic gelatino-silver brornoiodide emulsions of the type commonly utilized for X-rays, exposed in a sensitometer and processed as described in Example 1. Each of the samples were also subjected tothe Fingerprint Test described in Example 1. The results of the sensitometric tests and the fingerprint test are summarized by the data set out in Tables D and E below. With respect to the Fingerprint Tes, Table E indicates the degree of metallic silver deposited in the fingerprint areas after processing in terms relative to the control containing none of the feature addenda.

TABLE D (Developer A used) Cone. of Addenda Addenda Fresh Test 1 Week at (glmole 120 F., 50% RH.

AgX)

Speed 7 Fog Speed 7 Fog (1) Control 0 100 1.81 .04 120 1.58 .12 (2) Ethylenediaminetetraacetic acid tetrasodlum salt 1 97 1.74 .04 105 1.63 .10 (3) Ethylenediaminetetraacetic acid tetrasodium salt 4 2.00 .04 100 1.68 .08 (4) 1-Hydroxy-4- sultonaphthalene sodium salt 1 87 2. 00 .04 100 1.75 .08 (5) l-Hydroxylsulionaphthalene sodium salt 4 54 2. 00 .06 67 1.68 .14 (6) 1,8-Dihydroxy-3,

G-disulfonaphthalene disodium salt" 1 95 1.86 .04 115 1.65 .06 (7) 1,8-Dihydroxy-3,

fi-disulfonaphthalene disodiumsalt 4 91 1.98 .04 1.74 .06

TABLE E (Developer B used) (Ag Cone. of Fresh Test Deposited) Addenda Finger- Addenda (g./m0le print AgX) Test Speed 7 Fog Rel. to

Control (1) Control 0 100 1.90 .06 (2) Ethylenediamine- 1 1.80 .09 More.

tetraacetic acid tetrasodium salt. (3) Ethylenediamine- 4 126 l. 75 .09 More.

tetraacetic acid tetrasodium salt. (4) 1-Hydroxy-4-sulfo- 1 83 2.08 .05 Same.

naphthalene sodium salt. (5) 1-Hydroxy-4-sulfo- 4 53 2.13 .06 Same.

naphthalene sodium salt. (6) l,8-Dihydroxy-3,6- 1 87 2.14 .05 More.

disulfonaphthalcne disodium salt. (7) 1, 8-Dihydroxy-3,6- 4 83 2.24 .06 More.

disulionaphthalene disodium salt.

Substantial deposits of silver in the fingerprint area of the test sample resulted.

It should be noted from the data set out in Tables D and E that all of the addenda either desensitized the emulsion and/or did not significantly reduce coppercaused fog as demonstrated by the Fingerprint Test. In some instances the copper-caused fog was increased by the addenda, as indicated in Table E.

The term catechol used in the nomenclature of the present stabilizing addenda is equivalent to such commonly used terms as pyrocatechol," 1,2-benzenediol, 1,2-dihydroxybenzene and the like.

The invention has been described in considerable detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A photographic silver halide emulsion containing a stabilizing compound having a formula selected from the group consisting of and wherein X and Y are selected from the group consisting of a sulfo radical having the formula SO H, a Watersoluble salt of said sulfo radical and a hydrogen atom, and wherein at least one of X and Y is selected from the group consisting of said su-lfo radical and said salt of said sulfo radical.

3. A photographic silver halide emulsion containing about .25 to 20 grams per mole of silver halide in the emulsion of a stabilizing compound having the formula OI-I wherein X and Y are selected from the group consisting of a sulfo radical having the formula SO H, a watersoluble salt of said sulfo radical and a hydrogen atom, and wherein at least one of X and Y is selected from the group consisting of said sulfo radical and said salt of said sulfo radical.

4. A photographic gelatino-silver halide emulsion containing about 1 to 8 grams of 3,5-disulfocatechol disodium salt per mole of silver halide in the emulsion.

5. A photographic gelatino-silver halide emulsion containing about 1 to 8 grams of 2,3-dihydroxy-7-sulfonaphthalene sodium salt per mole of silver halide in the emulsion.

6. A photograhpie gelatino-silver halide emulsion containing about 1 to 8 grams of 4-sulfocatechol ammonium salt per mole of silver halide in the emulsion.

7. A photographic element comprising a photographic support having coated thereon a photographic emulsion as described in claim 1.

References Cited by the Examiner UNITED STATES PATENTS 2,221,793 11/ 1940 Gaspar. 2,591,542 4/1952 Harrirnan 96-1 11 2,675,318 4/1954 Russell et a1 9664 2,719,087 9/1955 Knox et a1. 96109 2,728,659 12/1955 Loria et al. 9610'9 FOREIGN PATENTS 1,112,282 8/1961 Germany.

129,092 6/1959 Russia.

NORMAN G. TORCHIN, Primary Examiner. 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING A STABLIZING COMPOUND HAVING A FORMULA SELECTED FROM THE GROUP CONSISTING OF 